9,9-bis (perfluoroalkyl) axanthene, 9-aryl-9-perfluoroalkylxanthene, monomers and polymers derived therefrom

ABSTRACT

Disclosed are rigid fluorinated monomers, their preparation, and polymers derived therefrom based on two novel tricyclic xanthene core systems, 9,9-bis-(perfluoroalkyl)xanthene (I) and 9-phenyl-9-perfluoro-alkylxanthene (II). The monomers have utility in the preparation of advanced high-performance polymers, particularly polyimides.

This application is a divisional of Ser. No. 07/527,740 filed May, 23,1990 now U.S. Pat. No. 5,051,520.

BACKGROUND OF THE INVENTION

The present invention relates to a new class of stiff, fluorinated,polycyclic xanthene monomers and polymers prepared therefrom.

The ever more stringent performance requirements of the electronicpackaging industry mandate the development of polymers with lowerdielectric constant and lower moisture absorption. Improvement in theseproperties has in the past been effected by the introduction of fluorineinto the polymer. Unfortunately, this was always accompanied bydeterioration of other properties, such as lowering of the glasstransition temperature, increasing the coefficient of thermal expansionand increasing solvent sensitivity.

SUMMARY OF THE INVENTION

Accordingly, the present invention relates to a new class of stiff,fluorinated monomers, based on two novel tricyclic xanthene coresystems, 9,9-bis(perfluoroalkyl)xanthene (I) and9-phenyl-9-perfluoroalkylxanthene (II) ##STR1## The monomers haveutility in the preparation of advanced high-performance polymers,particularly polyimides. The rigid core decreases the coefficient ofthermal expansion of the polymers while the fluorine substituentsimprove the dielectric constant and water absorption properties.

The novel invention compositions contain both a --CR_(f) R'_(f) -- or--C(phenyl)R_(f) -- bridge and a --O-- bridge.

According to the present invention there is provided a composition ofmatter, and the preparation thereof, of the formula ##STR2## wherein Ris selected from the group consisting of phenyl, substituted phenyl andperfluoroalkyl of 1 to 16 carbon atoms and Rf is perfluoroalkyl of 1 to16 carbon atoms.

In a further embodiment of the invention there is provided a compositionof matter, and the preparation thereof, of the formula ##STR3## whereinR is selected from the group consisting of phenyl, substituted phenyIand perfluoroalkyI of 1 to 16 carbon atoms, 16 carbon atoms: R_(f) isperfluoroalkyl of 1 to 16 carbon atoms; X is selected from the groupconsisting of H, CH₃, CO₂ H, COCl, NH₂ and NCO; Y is the same as X; andX and Y together are --CO--O--CO--. Another embodiment of the inventioncomprises a novel composition of the formula ##STR4##

The invention further relates to a polyimide polymer having thefollowing recurring structural unit ##STR5## wherein R is selected fromthe group consisting of phenyl, substituted phenyl and perfluoroalkyl of1 to 16 carbon atoms; R_(f) is perfluoralkyl of 1 to 16 carbon atoms; Ais a divalent radical containing at least two carbon atoms, the twoamino groups of said diamine each being attached to separate carbonatoms of said divalent radical; and n is a positive integer.

In the above definitions of R and R_(f) as perfluoroalkyl, a morepreferred number of carbon atoms is I to 18.

DETAILED DESCRIPTION OF THE INVENTION

The core ring systems (I) of the compositions of the invention can beprepared by using either a singlebridging or a double-bridging process.Scheme I depicts the preparation of9,9-bis(trifluoromethyl)-2,3,6,7-tetramethylxanthene (III) using bothprocesses.

In the double-bridging process both the ether bridge and the --C(CF₃)₂-bridge are introduced in a single step. This involves reaction ofhexafluoroacetone (HFA) with two molar equivalents of 3,4dimethylphenolto form the bridging --C(CF₃)₂ - linkage concurrent with intramoleculardehydration of the two hydroxyl groups ortho to the -C(CF3)2- bridge toform the xanthene ether link of (III). The reaction is run inhydrofluoric acid (HF) at temperatures ranging from 180° to 220° C.using a molar ratio of HF/HFA of 10 or more.

Other substrates such as resorcinol and 3-aminophenol may be used in thesimultaneous HFA bridging and cyclodehydration process. Reaction ofresorcinol with two molar equivalents of HFA at 220° C. (Scheme II)provided 9,9-bis(trifluoromethyl)-3,6-dihydroxy xanthene (VII).

Reaction of (VII) with two equivalents of p-nitrochlorobenzene indimethylacetamide solvent in the presence of potassium carbonatefollowed by hydrogenation of the dinitro precursor, provided9,9-bis-(trifluoromethyl)-3,6-bis(4-aminophenoxy)xanthene (VIII), a newdiamine monomer for use in polymer synthesis. A polyester (IX) derivedfrom reaction of (VII) with a mixture of isophthaloyl and terephthaloylchIorides was also found to have utility as a high flux membrane filmfor O₂ /N₂ separation.

The parent monomer, 9,9-bis(trifluoromethyl)xanthene (I, R_(f) =R'_(f)=CF₃) was prepared by reaction of (VlI) with sodium hydride and5-chloro-1-phenyl-lH-tetrazole to form9,9-bis(trifluoromethyl)-3,6-bis(1- phenyl-1H-tetrazolyl-5-oxy)xanthenewhich was catalytically reduced to (I) (Scheme IV). ##STR6##

In the single-bridging process for preparing the core ring systems(Scheme I), the ether linkage is first preformed separately followed byformation of the --C(CF₃)₂ -- bridge. Thus, (III) was prepared byreacting HFA in HF with 3,3'-di-o-xylyl ether (DXE), which alreadycontained the xanthese ether linkage, at temperatures ranging from 110°to 140° C. and an HF/DXE ratio of 8-20, perferably 10-15.

The single-bridging process is preferred to the double-bridging processfor preparing the core ring systems (I), since it requires lowerreaction temperatures, gives higher yeilds despite being a two-stepprocess, and generates fewer by-products.

Other aromatic ethers terminated by 3,4- dimethylphenoxy gropus can alsobe used in the single-bridging process. For example, p-tolylether(Scheme III, X) reacts with HFA in HF to provide 9,9-bis-(trifluoromethyl)-2,7- mimethylxanthene (XI). ##STR7##

Once produced, (III) (Scheme I) was readily oxidized to9,9-bis(trifluoromethyl)-2,3,67- xanthenetetracarboxylic aicd (IV),dehydrated to 9,9-bis(trifluoromethyl)xanthene tetracarboxylicdianhydride (V) and subsequently polymerized with4,4'-diaminodiphenylether to form polyimide (VI) (V-ODA). Analogouspolyimides were obtained using 3,4'-diaminodiphenylether, (I)-ODA andparaphenylenediamine. Oxidation of (III) to the tetraacid (IV) wasperformed using potassium permanganate in aqueous pyridine. Othermethods, such as Mn/Co catalyzed oxidation with oxygen or air, oroxidation with nitric acid can also be used.

Conversion of (IV) to the dianhydride (V) can be effected thermally, byboiling in acetic anhydride, or by heating a slurry of (IV) inchloroform with excess thionyl chloride. Thermal conversion by heatingat 20° C overnight is preferred. The polyimide (VI) was prepared byreacting the dianhydride (V) with a substantially equimolar amount of4,4'-diaminodiphenylether in dimethylacetamide to form a polyamide acidand then thermally converting the polyamide acid to the polyimide.

In similar fashion (XI) (Scheme III) was oxidized with permanganate to9,9-bis(trifluoromethyl)xanthene2,7-dicarboxylic acid (XII) and thenreacted with thionyl chloride to provide9,9-bis(trifluoromethyl)-xanthene-2,7-dicarbonyl chloride (XIII). Thediacid chloride was subsequently reacted with sodium azide by theCurtius Reaction to provide9,9-bis(trifluoromethyl)xanthene-2,7-diisocyanate (XIV) which washydrolyzed to 9,9-bis(trifluoromethyl)xanthene-2,7-diamine (XV).##STR8##

The core ring system (II) was prepared in similar fashion using thesingle-bridging process and RCOR_(f) insteand of HFA to provideanalogous compounds containing a --CRR_(f) -- bridge instead of a--C(CF₃)₂ -- bridge. Compounds of the structure RCOR_(f) include thosewherein R is phenyl or substituted phenyl and R_(f) is CF₃, C₂ F₅, C₃ F₇and C₈ F₁₇.

For example, the reaction of 3,3'-di-o-xylyl ether (DXE) withtrifluoroacetylbenzene (R=phenyl, R_(f) =CF₃) in HF at 140° C. provided9-phenyl-9-trifluoromethyl-2,3,6,7-tetramethylxanthene (XVI) (Scheme V).Oxidation of (XVI) with potassium permanganate gave9-phenyl-9-(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic acid (XVII)which was thermally converted to 9-phenyl-9-trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic dianhydride (XVIII) by heating under vacuum at250° C.

The parent monomer (II, R_(f) =CF₃) was prepared (Scheme VI) using thesingle-bridging process by reaction of p-tolyl ether (X) andtrifluoromethylphenyl ketone in HF at 130° C. to provide9-phenyl-9-trifluoromethyl-2,7-dimethylxanthene (XIX), followed byoxidation to the dicarboxylic acid (XX) and catalytic decarboxylation to(II). The diacid (XX) could also be converted to the diacyl chloride(XXI), then to the diacyl azide and, finally, to the diisocyanate (XXII)as previously described.

Polyimides encompassed by the present invention include those having therecurring structural unit ##STR9## wherein R is selected from the groupconsisting of phenyl, subtituted phenyl and perfluoroalkyl of 1 to 16carbon atoms; R_(f) is perfluoroalkyl of 1 to 16 carbon atoms (and morepreferably 1 to 8 carbon atoms); A is a divalent radical containing atleast two carbon atoms, the two amino groups of said diamine each beingattached to separate carbon atoms of said divalent radical and n is apositive integer.

The polyimides display outstanding physical properties making themuseful as shaped structures such as self-supporting films, fibers andfilaments. The structures are characterized by high tensile properties,desirable electrical properties, stability to heat and water and verylow coefficient of thermal expansion. The polyimides are generallyprepared by reacting dianhydrides (V) or (XVIII) with an aromaticdiamine in an inert organic solvent to form a polyamide acid solutionand subsquently converting the polyamide-acid to polyimide essentiallyas described in U.S. Pat. No. 3,179,614; U.S. Pat. No. 3,179,630 andU.S. Pat. No. 3,179,634, the disclosures of which are incorporatedherein by reference.

If desired, dianhydrides (V) or (XVIII) can also be blended with from 15to 85 mole % of other dianhydrides, such as pyromellitic dianhydride;2,3,6,7-naphthalene tetracarboxylic dianhydride; 3,3',4,4'-biphenyltetracarboxylic dianhydride; 1,2,5,6-naphthalene tetracarboxylicdianhydride; 2,2',3,3'-biphenyl tetracarboxylic dianhydride;3,3',4,4'-benzophenone tetracarboxylic dianhydride;2,2-bis(3,4-dicarboxyphenyl) propane dianhydride;bis(3,4-dicarboxyphenyl) sulfone dianhydride; 3,4,9,10-perylenetetracarboxylic dianhydride; bis(3,4-dicarboxyphenyl) propanedianhydride; 1,1-bis-(2,3-dicarboxyphenyl) ethane dianhydride;1,1-bis-(3,4-dicarboxyphenyl) ethane dianhydride;bis-(2,3-dicarboxyphenyl) methane dianhydride; bis-(3,4-dicarboxyphenyl)methane dianhydride; oxydiphthalic dianhydride; bis(3,4-dicarboxyphenyl) sulfone dianhydride; and the like.

Suitable diamines for use in the polyimide compositions of the inventioninclude:

meta-phenylenediamine;

paraphenylene diamine;

4,4'-diamino-diphenyl propane;

4,4'-diamino-diphenyl methane;

benzidine;

4,4'-diamino-diphenyl sulfide;

4,4'-diamino-diphenyl sulfone;

3,3'-diamino-diphenyl sulfone;

4,4'-diamino-diphenyl ether;

2,6-diamino-pyridine;

bis-(4-amino-phenyl)diethyl silane;

bis-(4-amino-phenyl)phosphine oxide;

bis-(4-amino-phenyl)-N-methylamine;

1,5-diamino-naphthalene;

3,3'-dimethyl-4,4'-diamino-biphenyl;

3,3'-dimethoxy benzidine;

2,4-bis(beta-amino-t-butyl)toluene;

bis-(para-beta-amino-t-butyl-phenyl)ether;

para-bis(2-methyl-4-amino-pentyl)benzene;

para-bis-(1,1-dimethyl-5-amino-pentyl)benzene;

m-xylylene diamine;

p-xylylene diamine;

bis(para-amino-cyclohexyl)methane;

hexamethylene diamine;

heptamethylene diamine;

octamethylene diamine;

nonamethylene diamine;

decamethylene diamine;

3-methylheptamethylene diamine;

4,4-dimethylheptamethylene diamine;

2,11-diamino-dodecane;

1,2-bis-(3-amino-propoxy)ethane;

2,2-dimethyl propylene diamine;

3-methoxy-hexamethylene diamine;

2,5-dimethylhexamethylene diamine;

2,5-dimethylheptamethylene diamine;

5-methylnonamethylene diamine;

1,4-diamino-cyclohexane;

1,12-diamino octadecane;

H₂ N(CH₂)₃ O(CH₂)₃ NH₂ ;

H₂ N(CH₂)₃ S(CH₂)₃ NH₂ ;

H₂ N(CH₂)₃ N(CH₃)(CH₂)₃ NH₂ ;

and mixtures thereof.

Useful solvents include normally liquid N,N-dialkylcarboxylamides,generally. Preferred solvents include the lower molecular weight membersof such carboxylamides, particularly N,N-dimethylformamide andN,N-dimethylacetamide. Other useful compounds of this class of solventsare N,N-diethylformamide and N,N-diethylacetamide. Other solvents whichmay be used are dimethylsulfoxide, N-methyl-2-pyrrolidone, tetramethylurea, dimethylsulfone, hexamethylphosphoramide, tetramethylene sulfone,and the like. The solvents can be used alone, in combinations with oneanother or in combinations with poor solvents such as benzene,benzonitrile, dioxane, etc. The amount of solvent used preferably rangesfrom 75 to 90 weight % of the polyamic acid, since this concentrationhas been found to give optimum molecular weight.

Conversion of the polyamic acid to polyimide can be accomplished byeither a thermal conversion or a chemical conversion process. Accordingto the thermal conversion process, the polyamic acid solution is cast ona heated conversion surface, such as a metal drum or belt, and heated ata temperature of above about 50° C. to partially convert the polyamicacid to polyimide. The extent of polyamic acid conversion depends on thetemperature employed and the time of exposure, but, generally about 25to 95% of amic acid groups are converted to imide groups. The partiallyconverted polyamic acid is then heated at or above 220° C. to obtaincomplete conversion to the polyimide.

In the chemical conversion process, the polyamic acid solution is firstchilled to about 10° C. to -10° C. and polyamic acid conversionchemicals are added. The polyamic acid conversion chemicals are tertiaryamine catalysts and anhydride dehydrating materials. The preferredanhydride dehydrating material is acetic anhydride and is used in slightmolar excess of the amount of amic acid groups in the polyamic acid,typically about 2-2.5 moles per equivalent of polyamic acid. Acomparable amount of tertiary amine catalyst is used. Besides aceticanhydride, other operable lower fatty acid anhydrides include propionic,butyric, valeric, mixed anhydrides of these with one another and withanhydrides of aromatic monocarboxylic acids, for example, benzoic acid,naphthoic acid, and the like, and with anhydrides of carbonic and formicacids, as well as aliphatic ketenes (ketene and dimethyl ketene).Ketenes may be regarded as anhydrides of carboxylic acids 5 derived fromdrastic dehydration of the acids.

The preferred tertiary amine catalysts are pyridine and beta-picolineand they are used in an amount of about one mole per mole of anhydridedehydrating material. Tertiary amines having approximately the sameactivity as the preferred pyridine and beta-picoline may also be used.These include 3,4-lutidine; 3,5-lutidine; 4-methylpyridine; 4-isopropylpyridine; N-dimethylbenzylamine; isoquinoline; 4-benzylpyridine, andN-dimethyldodecylamine. Trimethylamine and triethyl amine are moreactive than those amines listed above and can be used in smalleramounts.

The polyamic acid conversion chemicals react at about room temperatureor above to convert polyamic acid to polyimide. The chemical conversionreaction occurs at temperatures from 10° to 120° C., with the reactionbeing very rapid at the higher temperatures and very slow at the lowertemperatures. Below a certain temperature, polyamic acid chemicalconversion comes to a practical halt. This temperature is generallyabout 10° C. It is important, therefore, that the polyamic acid solutionbe chilled below this temperature before adding the polyamic acidconversion chemicals and that the temperature of the solution, withconversion chemicals, be maintained below this temperature duringextrusion or casting.

The treated, chilled, polyamic acid solution is cast or extruded onto aheated conversion surface whereupon some of the solvent is evaporatedfrom the solution, the polyamic acid is partially chemically convertedto polyimide, and the solution takes the form of a polyamicacid-polyimide gel. Conversion of amic acid groups to imide groupsdepends on contact time and temperature but is usually about 25 to 95%complete.

The gel is subsequently dried to remove the water, residual solvent, andremaining conversion chemicals, and the polyamic acid is completelyconverted to polyimide. The drying can be conducted at relatively mildconditions without complete conversion of polyamic acid to polyimide atthat time, or the drying and conversion can be conducted at the sametime using higher temperatures. Preferably, high temperatures are usedfor short times to dry the film and convert it to polyimide in the samestep. It is preferred to heat the film to a temperature of 200°-450° C.for 15 to 400 seconds.

The xanthene core monomers (I) and (II) are particularly useful for thepreparation of polyimide polymers. The diacid chlorides, diacids,diisocyanates and diamine monomers of the present invention can also beused to prepare polyamides, polyesters, polycarbonates and polyurethanesby techniques which are well-known in the art.

The advantageous properties of this invention can be observed byreference to the following examples which illustrate, but do not limit,the invention. All parts and percentages are by weight unless otherwiseindicated.

All reagents used were commercial materials, unless otherwise indicated.IR spectra were measured as Nujol mulls, or as polyimide films, on aPerkin-Elmer Grating IR Spectrophotometer Model 457. NMR spectra weredetermined on the GE QE-300 instrument, using deuterochloroform assolvent and tetramethylsilane as internal standard.

Aromatic Ether Precursors

All aryl ethers were prepared by the reaction of the appropriatepotassium aryloxide with a mono- or dibromoaryl precursor, using NMP assolvent. The method is illustrated by the preparation of 3,3'-di-o-xylylether (DXE).

3.3'-di-o-xylyl Ether (DXE)

In a 3-L four-neck flask was placed 1.2L toluene, 500 g (4.1 mole) of3,4-dimethylphenol, and 227 g (4.1 mole) KOH pellets. The mixture wasstirred with an efficient mechanical stirrer and refluxed, water beingremoved via a Dean-Stark trap. When all the water was removed, at whichpoint the potassium phenolate salt started to crystallize out, about 500ml toluene was distilled out (leaving enough toluene, so that the slurrywas still stirrable). About 500 ml N-methylpyrrolidone (NMP) was added,along with 750 g (4.1 mole) -bromo-o-xylene, and 100 g copper powder.The reaction mixture was heated again, and remaining toluene wasdistilled out through a tall Vigreux column. When all the toluene hadbeen distiIled out, and the temperature in the flask reached about 200°C., the distillation column was replaced with a condenser, and thevigorously stirred mixture was refluxed overnight. The mixture wasfiltered through a bed of Celite, and the flask was rinsed with someDMF, which was used to wash the filter cake. The filtrate wasconcentrated at atmospheric pressure, until DMF and most of the NMP wasdistilled out, then distillation was continued at reduced pressure,collecting the product boiling at 140°-145° C./ 1.4-1.7 Torr. The stillwarm fraction was poured into 500 ml stirred methanol; this resulted inprecipitation of a crystalline product, which was filtered off andwashed with methanol. A second crop was obtained from the filtrate for atotal yield in the 360-420 g (55-65%) range, taking into considerationthat the starting -bromo-o-xylene was only 70% pure. NMR of the titlematerial: d 7.03, d 6.80, dd 6.73, s 2.19 in the correct 1:1:1:6 ratio;the two non-identical methyl groups show up as a singlet. From thefiltrates one could distill a fraction boiling where the main productboiled. This oil could not be crystallized, and by NMR consisted of anapproximately 50/50 mixture of DXE and the mixed ether arising from theisomeric 3-bromo-oxylene, which comprised almost 30% of the startingmaterial.

Di-p-tolyl Ether (X)

Obtained in 56% yield; NMR: d 7.10, d 6.87, s 2.30 ppm in 2:2:3 ratio.

EXAMPLE 1 9,9-Bis(trifluoromethyl)xanthene (I, R_(f) =R'_(f) =CF₃)

A. 9,9-bis(trifluoromethyl)-3,6-bis(1-phenyl1H-tetrazolyl-5-oxy)xanthene

In 250 ml of dry diglyme was stirred at room temperature 5 g of 50%sodium hydride in mineral oil, plus 17.5 g (0.05 mole)9,9-bis(trifluoromethyl)-3,6dihydroxyxanthene (VII). The hydrogenevolved was measured by a wet-test meter. When hydrogen evolutionstopped, 18.1 g (0.1 mole) of 5-chlorophenyl-lHtetrazole was added inone portion, and the mixture was stirred and gently heated until thesecond evolution of hydrogen stopped. The flask contents were drownedwith stirring in 2.5L ice water. A solid separated, which was filteredoff, dissolved in methylene chloride, and filtered through a bed ofalumina. The filtrate was stripped to dryness, and the residue wasstirred with methanol, and was filtered. There was obtained a total of27.1 g (86%) of a solid with a sharp IR spectrum, which contained no OHor CO peaks. The NMR spectrum was consistent with the assignedstructure: d 7.97, dd 7.78, m 7.6, d 7.45, dd 7.34 in 1:2:3:1:1: ratio,assigned to the 1H, phenyl ortho H's, phenyl m and p H's, 4H, and 2H,respectively.

B. 9,9-bis(trifluoromethyl)xanthene (I)

A mixture of 25 g9,9-bis(trifluoromethyl)-3,6-bis-(1-phenyl-1H-tetrazolyl-5-oxy)xantheneand 6 g of 5% palladium on carbon in 250 ml THF was heated in a shakertube at 400 psi of hydrogen for 16 hrs at 100° . The pressure dropped by42 psi which occurred within the first 9 hrs, and did not changethereafter. The reaction mixture was filtered, and the residue wasfractionally distilled. The product distilled at 105°/1.2 Torr and wasobtained in 5.0 g (39%) yield. It was recrystallized from methanol andpurified further by vacuum sublimation. M.p. 74°-75° C. NMR: dd 7.88; td7.44 plus overlapping td and dd 7.3-7.4 in 1:1:1:1 ratio; C¹³ NMR: m52.5 (bridgehead C), 110.0 (C next to the bridge), 117.6 (4C), 123.3(2C), quartet (J =287 Hz) 124.3 (CF₃), 130.2 (lC), 131.5 (3C) and 151.0(C next to 0) ppm, in agreement with the assigned structure. The massspectrum of (I) showed the molecular formula to be C₁₅ H₈ F₆ O, and hada parent peak at 318, plus prominent peaks at 249 (parent minus CF₃),199 (parent minus C₂ H₅), 100 (C₂ F₄) and 69 (CF₃). Elemental analysis:Calc. for C₁₅ H₈ F₆ O: C 56.5; H 2.52; Found: C 56.6; H 2.91.

EXAMPLE 2 9-Phenyl-9-trifluoromethylxanthene (II, R_(f) =CF₃)

A 6 g sample of 9-phenyl-9-trifluOrOmethylxanthene2,7-dicarboxylic acid(XX) was stirred and refluxed in ml quinoline along with 11 g of copperpowder, the emanating gas being measured by a wet-test meter. Thetheoretical amount of CO₂ was evolved in two hours. The reaction mixturewas cooled, filtered through a bed of Celite into 800 ml of water,acidified with 100 ml of concentrated hydrochloric acid, and leftstanding overnight. The supernantant liquid was decanted, and theresidue was taken up in methylene chloride, and filtered through a bedof alumina. The solvent was stripped, the residue was stirred withmethanol, and was filtered, yielding 3.1 g (66%) of a white solid. Itwas recrystallized from methanol; m.p. 89°-90°. The IR spectrum wassharp with no OH or CO bands. The NMR spectrum was confirmatory, withthe following peaks: d 7.42; m 7.3-7.4; d 7.19, td 6.96, d 6.87 in2:5:2:2:2 ratio. The compound was analyzed by mass spectrometry whichshowed the parent ion at 326, along with other Peaks, the strongestbeing at 257 (parent minus trifluoromethyl), and also at 249 (parentminus phenyl), and 199 (parent minus phenyl and minus difluorocarbene).The mass spectrum confirmed the molecular formula as C₂₀ H₁₃ F₃ O.

EXAMPLE 3 9,9-Bis(trifluoromethyl)-2,3,6,7-tetramethylxanthene (III)Double Bridging Process

A mixture of 330 g (2.7 moles) 3,4-dime:hylphenol, 225 g (1.35 moles)HFA and 300 g (15 moles) HF was shaken in an autoclave for 15 hrs at220°. The reaction mixture was poured into a one-gallon polyethylenejar, half-filled with ice-water and containing excess sodium hydroxide.The product was extracted with methylene chloride, the extracts werefiltered through alumina, and stripped. Distillation of the residue invacuo gave several fractions. The fraction, boiling at 190°-210°/1 Torrwas chromatographed on alumina, packing and eluting with methylenechloride. The orange band was collected, and the fraction was stripped.Stirring of the residue with excess methanol, filtration, washing of thesolid with more methanol, and air-drying gave 86 g (17%) of (III) whichmelts at 214°-215°, and sublimes readily in vacuo at 180° /1 Torr; itcan be recrystallized from toluene or heptane, but is sparingly solublein methanol. Analysis: Calc. for C₁₉ H₁₆ F₆ O: C, 61.0; H, 4.28; F,30.5; Found: C, 61.3, H, 4.40; F, 30.7% NMR: s 7.57, s, 6.95, s, 2.26ppm in 1:1:6 ratio

Single-Bridging Process

A mixture of 200 g (0.88 mole) DXE, 150 g (0 88 mole) HFA, and 236 g(11.8 moles) HF was heated at 120° for 8 hrs in a shaker tube. Afterventing excess HF, the tube contents were drowned in a one-gallonpolyethylene jar containing 2L ice-water, and 500 ml of 50% NaOH. Theshaker tube was rinsed out with methylene chloride, and the washingswere added to the jar. Most of the aqueous layer was decanted, and theproduct was 5 extracted wth 3-4L of methylene chloride. The slurry wasfiltered once through a bed of Celite to remove a pasty sludge and thelayers were separated. The organic layer was filtered through a layer ofalumina, and then stripped to dryness. The reddish crystalline residue30 was dissolved in 150-200 ml of boiling toluene, partially cooled anddiluted with 500 ml methanol, which resulted in rapid crystallization.The solid was filtered, washed with methanol until the washings were nolonger red, and was air-dried, yielding 95-105 g (29-32%) of pale creamysolid. The filtrates were stripped to dryness, and the residue wasdistilled over a short-path column. Pale orange material boiling at200-210°/1 Torr was collected, dissolved in minimum quantity of boilingtoluene and diluted with methanol, yielding another 15-20 g of product,for a total yield in the 33-41% range.

EXAMPLE 4 9.9-Bis(trifluoromethyl)-2,3,6,7-xanthene-tetracarbosylic acid(IV)

9,9-Bis(trifluoromethyl-2,3,6,7-tetramethylxanthene (III) (20 g, 0.053mole) was reluxed in a mixture of 40 ml pyridine and 200 ml water withrapid mechanical stirring, and 50 g (0.316 mole) potassium permanganatewas added in portions through the top of the condenser. After additionwas complete, the slurry was refluxed for hr. The mixture was filteredhot through Celite, and concentrated down to about 50 ml. A mixture of35 g NaOH and 535 ml water was added, and the oxidation was repeated,using 45 g (0.28 mole) KMnO₄. After the second oxidation, excesspermanganate was destroyed with isopropyl alcohol. The mixture wasfiltered through Celite, and the filtrate was acidified with sulfuricacid. This produced a white precipitate, which was filtered, and washedthoroughly with water. The tetraacid (IV) was dried in a convection ovenovernight at 150° and was obtained in 16 g yield (61%). It was used forconversion to the anhydride, without further purification.

EXAMPLE 5 9,9-Bis(trifluoromethyl)- 2,3,6,7-xanthenetetracarboxylicDianhydride (V)

9,9- Bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxylic acid (IV) wasconverted to dianhydride (V) by drying overnight in a convection oven at220°. Even during drying at 150°-180° some conversion to the anhydridetook place. The dehydration could be followed by means of changes in thecarbonyl region from those of tetraacid (IV) (descending pattern at1860, 1780, 1740 and 1710 cm⁻¹) to those of dianhydride (V) (1860, 1775vs). Both, TGA and DSC data for (IV) indicate dehydration occurringaround 240°, and the second event (melting/sublimation of (V)) takingplace around 355°-360°.

Tetraacid (IV) could also be dehydrated by acetic anhydride; refluxingwith excess acetic anhydride for one hour usually sufficed to dehydrate(IV). Dianhydride (V) was essentially insoluble in acetic anhydride, andcould be isolated by simple filtration and drying of the slurry.

Another method, used for dehydrating tetraacid (IV) involved refluxing aslurry of (IV) in chloroform with excess thionyl chloride for two hours.Again, since dianhydride (V) was essentially insoluble in chloroform,simple filtration and washing with chloroform yielded the product.

Purification of dianhydride (V) could not be achieved byrecrystallization since it has very low solubility in acetic acid/aceticanhydride mixtures. It could, however, be sublimed at 250° /1 Torr. Thiswas done conveniently in small sublimer tubes, where fairly largecrystals with a slight yellowish cast could be grown. Pure dianhydride(V) melts in a capillary at 355-356°. IR (Nujol mull): 1860, 17775 (vs)cm⁻¹. It was too insoluble for determining its NMR spectrum. Analysis:Calc. for C₁₉ H₄ F₆ O₇ : C, 49.8; H, 0.87; F,

24.9; Found: C, 50.1; H. 1.11; F, 24.9%.

EXAMPLE 6 Polyimide films derived from 9.9-bis(trifluoromethyl)xanthenetetracarboxylic dianhydride (V)

In a flame-dried and nitrogen-flushed 500 ml roundbottom flask wasplaced 5.00 g (0.025 mole) of 4,4'-diaminodiphenylether (ODA) which wasdissolved in 200 ml dry NMP. To the stirred solution was added inportions 1.45 g (0 025 mole) of9,9-bis(trifluoromethyl)xanthenetetracarboxylic dianhydride (V). Most ofthe I0 dianhydride (V) dissolved within one hour, but the rest only uponstirring overnight. Dianhydride (V) was doubly sublimed, but still notvery pure, as it contained sublimation residue particles which adheredto the sublimate electrostatically. The 8% by weight solution ofpolyamic acid was converted into a film by [either casting or spincoating, and cured at 350°-400° C. in air. The (V)-ODA film was verythin, but did have a sharp IR, and was characterized by imide peaks at1785 and 1730 (vs) cm⁻ 1.

More concentrated solutions, up to 27% solids, were prepared as above,and produced thicker (V)-ODA films with the properties listed in TableI.

In similar fashion, polyimide films were prepared from9,9-bis(trifluoromethyl)xanthenetetracarboxylic ianhydride (V) andparaphenylenediamine (PPD), 3,4-diaminodiphenyl ether (3,4'-ODA),resorcinol oxydianiline (RODA) and (I)-ODA. Physical properties of thefilms are given in Table I.

                                      TABLE I                                     __________________________________________________________________________    PHYSICAL PROPERTIES OF POLYIMIDE FILMS FROM                                   9,9-BIS (TRIFLUOROMETHYL) XANTHENE TETRACARBOXYLIC DIANHYDRIDE (V)                   Spin or                                                                           Final Temp.                                                                          Cure Time                                                                           Thickness*                                                                          Tensile Strength                                                                       Elastic Modulus                                                                       Elongation                     Film   Cast                                                                              (°C.)                                                                         (min.)                                                                              (um)  (MPa)    (GPa)   (%)                            __________________________________________________________________________    (V)-ODA                                                                              Spin                                                                              350    60    10    115 ± 8                                                                             1.6 ± 0.1                                                                          20 ± 6                             Spin                                                                              350    60    23 ± 2                                                                           110 ± 6                                                                             1.5 ± 0.2                                                                          20 ± 6                             Cast                                                                              350    60     6 ± 1                                                                           115 ± 9                                                                             1.3 ± 0.1                                                                          21 ± 6                             Cast                                                                              350    60    18 ± 2                                                                           97 ± 5                                                                              1.2 ± 0.1                                                                          15 ± 2                             Cast                                                                              350    60    27 ± 1                                                                            82 ± 18                                                                            1.8 ± 0.1                                                                           6 ± 3                      (V)-3,4'-ODA                                                                         Spin                                                                              350    60    10    83 ± 6                                                                              1.4 ± 0.1                                                                           8 ± 1                      (V)-PPD                                                                              Spin                                                                              350    60     8    147 ± 10                                                                            4.3 ± 0.2                                                                          4                                     Spin                                                                              350    60    47 ±  7                                                                          208 ± 21                                                                            4.0 ± 0.2                                                                          10 ± 1                             Spin                                                                              400    60     8.3 ± 0.3                                                                       280 ± 21                                                                            7.1 ± 0.3                                                                           7 ± 2                      (V)-RODA                                                                             Spin                                                                              400    60     6.5 ± 0.7                                                                       110 ± 19                                                                            2.3 ± 0.2                                                                           7 ± 3                      (V)-(I)ODA                                                                           Spin                                                                               40    60     8.2 ± 0.3                                                                       126 ± 15                                                                            2.2 ± 0.2                                                                          16 ± 8                      __________________________________________________________________________     *Typical thickness deviations for cast films were ± 8 to 12%; for spin     coated films ± 0.5 to 2%                                              

EXAMPLE 7 9,9-Bis(trifluoromethyl)-2,7-dimethylxanthene (XI)

A mixture of 200 g (1 mole) p-tolyl ether, 166 g (1 mole) HFA and 220 g(11 moles) HF was heated at 140° for 8 hrs in a shaker tube. Afterdistilling out residual HF, the tube contents were poured into excessice-cold dilute NaOH. The product was extracted with methylene chloride,the extracts were passed through a short alumina column, and stripped todryness. The residue was distilled in vacuo, collecting the cut boilingaround 110° /1.7 Torr, which partly solidified on standing. It wasstirred with methanol, filtered, washed with more methanol, and dried,yielding a total of 24.3 g (7%) of (XI) as white crystals in two crops(14.5 and 9.8 g). 9,9-Bis(trifluoromethyl)-2,7-dimethylxanthene (XI) isquite volatile, and sublimes in vacuo below 100° , and melts at 136-137°. Analysis: Calc. for C₁₇ H₁₂ F₆ O: C, 59.0; H, 3.47; F, 33.0; Found: C,59.3; H, 3.56; F, 33.5%. The NMR spectrum was confirmatory: s 7.65, dd7.23, d 7.06, s 2.35 ppm in 1:1:3 ratio.

EXAMPLE 8 9,9-Bis(trifluoromethyl)xanthene-2,7-dicarboxylic acid (XII)

To a refluxing solution of 34.6 g (0.1 mole) of9,9-bis(trifluoromethyl)-2,7-dimethylxanthene (XI) in ml pyridine and100 ml water was added in portions g (0.35 mole) potassium permanganate.After 90 min reflux (as the permanganate color was discharged, and Mn02precipitated) the mixture was filtered, and the filtrate was boiled downto about 100 ml. The residue was diluted with 70 g of 50% NaOH and 400ml water, and oxidized with an additional 55 g KMnO₄ as above.Filtration of the mixture, and acidification with sulfuric acid yieldeda white precipitate, which was filtered, and washed well with water. Thematerial melts at 344°-347° in capillary (DSC shows a peak at 53°) andis sublimable in vacuo. Analysis: Calc. for C₁₇ H₈ F₆ O₅ : C, 50.3; H,1.97; F, 28.1; Found: C, 51.2; H, 1.75; F, 25.8. IR: 1700 00 (vs), 1620,1560 cm⁻¹.

EXAMPLE 9 9,9Bis(trifluoromethyl)xanthene-2,7-dicarbonyl chloride (XIII)

A mixture of 20 g 9,9-bis(trifluoromethyl)xanthene-2,7-dicarboxylic acid(XII), 250 ml chloroform and 20 ml (excess) thionyl chloride was stirredand refluxed until the slurry became a pale yellow solution (4 hrs). Thevolatiles were distilled out, ultimately at house vacuum, and theresidue (16 g, 73%) was purified by sublimation. The product (XIII) canalso be recrystallized from toluene/heptane. M.p. 216°-218° IR: 1750(vs) cm⁻¹. NMR: s 8.76, dd 8.31, d 7.44 in 1:1:1 ratio. Analysis: Calc.for C₁₇ H₆ C1₂ F₆ O₃ : 1.35; Cl 16.0; F 25.7; Found: C 46.1; H 1.22; Cl15.9; F 26.3.

EXAMPLE 10 9,9-Bis(trifluoromethyl)xanthene-2.7-diisocyanate (XIV)

A mixture of 4.43 g (0.01 mole) of9,9-bis(trifluoromethyl)xanthene-2,7-dicarbonyl chloride (XIII), 4.43 g(0.07 mole) technical sodium azide and 100 ml toluene was refluxedovernight, the emanating nitrogen being measured by a wet-test meter. Atotal of 0.42L (84% theory) was evolved. The mixture was filtered, andthe filtrate evaporated, yielding 2.4 g (60%) of waxy solid, with astrong NCO band at 2270 cm⁻¹. lt was sublimed in vacuo; m.p. 105°-107°.

EXAMPLE 11 9,9-Bis(trifluoromethyl)xanthene-2,7-diamine (XV)

A mixture of 10 g crude 9,9-bis(trifluoromethyl)-xanthene-2,7-dicarbonylchloride (XIII) and 10 g sodium azide was stirred and refluxed overnightin 150 ml toluene. The mixture was filtered, and stripped to dryness,and the residue was refluxed for 3 hrs in 100 ml 20% hydrochloric acid.The slurry was filtered, and the filtrate was basified yielding somesolid. The initial solid from the acid solution was stirred in excessaquomethanolic sodium hydroxide, and filtered. After drying, andcombining the two solids, there was obtained 4.1 g (52%) of the diamine(XV). It can be distilled in a sublimation tube, and solidifies oncooling. After recrystallization from heptane, the product melted at137°-138° , and had amine bands at 3470, 3400, 3370, 3350 and 3230 cm⁻¹.NMR:d (small J) 7.13, d (large J) 6.98, dd 6.80 and broad peak around3.5 ppm in 1:1:1:2 ratio, corresponding to the 1, 3, 4, and aminoprotons, respectively.

EXAMPLE 12 9,9-Bis(trifluoromethyl)-3,6-dihydorxyxanthene (VII)

A mixture of 300 g (2.7 moles) resorcinol, 225 g (1.35 moles) HFA and300 g (15 moles) HF was heated in a shaker tube to 220° and kept therefor 15 hrs. After distilling out excess HF, the reaction mixture waspoured into a one-gallon polyethylene jar, half-filled with ice-water,and containing 200 g potassium acetate. The lumpy, and sometimes sticky,reddish-brown solid was isolat®d by filtration, washed with water, andair dried (yield of this crude solid averaged about 450 g). 1t wasplaced in a 4L beaker, and the product was extracted with 2L of boilingtoluene, stirring well with a large metal spatula. The extracts weredecanted hot from the red tar insoluble in toluene (but very soluble inacetone), and filtered through a 2-cm bed of Celite. On cooling, ambercrystals of (VII) grew from the solution. They were filtered off, and asecond crop was obtained by concentrating the mother liquors, andcooling. Total yield for a number of runs averaged about 100 g (20%).After repeated recrystallization from toluene, using Darco, paleyellowish platelets were obtained, m.p. 209°-210°. Analysis: Calc. forC₁₅ H₈ F₆ O₃ : C, 51.4; H, 2.29; F, 32.6; Found: C, 51.3; H, 2.45; F,32.9%. The IR spectrum of (VII) has strong phenolic OH at 3100-3500cm⁻¹, which disappears on acetylation (see below). NMR (in (CD3)2CO,since CDC13 solubility was very low): d 7.70; dd 6.65; OH singlet 5.42ppm in 1:2:1 ratio.

Since neither chromatography, nor repeated recrystallization, usingDarco, succeeded in removing the yellowish color, the diol was purifiedby conversion to the diacetate, which was purified by short-path

distillation (main cut b.p. 195°-204°/1.4 Torr.). The diacetate wasrecrystallized from toluene/heptane yielding snow white crystals, andwas then hydrolyzed by heating overnight in methanol with an equivalentamount of NaOH. The pale amber solution was stripped, the residue wasstirred with 300 ml hot water, filtered, the solid was washed repeatedlywith hot water and was then air-dried. Yield was quantitative.

EXAMPLE 13 9,9-Bis(trifluoromethyl)-3.6-bis(4-amino-phenoxy)xanthene(VIII)

A mixture of 51.4 g of 9,9-bis(trifluoromethyl)-3,6-dihydroxyxanthene(VII) (0.147 mole), 46.3 g p-nitrochlorobenene (0.294 mole), 120 ml DMACand 44.7 g anhydrous potassium carbonate (0.32 mole) was refluxed 4.5hrs. The mixture was filtered, and the solid was washed with copiousamounts of water, and then with methanol. After drying there wasobtained a total of 83.7 g (96%) of crude product. The NMR spectrum ofthe dinitro compound was in agreement with the structure: the A₂ B₂pattern of the p-nitrophenoxy group as doublets at 8.28 and 7.18, d (b,large J) 7.92 (1-H), dd 6.94 (2-H) and d (small J) 6.87 (4-H ppm, in thecorrect 1:2:1:1 ratio.

The crude dinitro compound (75 g) was hydrogenated at 50° in 400 mlethanol, using 3 g of 10% Pd/C catalyst at 500 psi hydrogen pressure,until there was no further pressure drop. The reduction mixture wasfiltered, the filtrate was concentrated down to 300 ml, cooled, andacidified with 280 ml of concentrated hydrochloric acid. The aminehydrochloride was filtered, washed with 20% hydrochloric acid, and driedunder a nitrogen blanket. After drying in a vacuum oven, there wasobtained 68 g of the dihydrochloride. It was dissolved in aqueousmethanol, and the solution was made basic with sodium hydroxide, whichliberated the diamine (XIII). It was isolated by filtration, and washedwith much water. After drying under nitrogen, there was obtained 58 g ofwhite solid. The material softens around 89°, and melts at 124° turningdark.

It was purified by distillation in vacuo, and boiled at 305°-307°/1.5Torr. The NMR spectrum was confirmatory: A₂ B₂ pattern as doublets at8.27 and 7.18, the 4-H as broad d (large J) 7.92, 3-H as dd 6.94, 1-H asd (small J) 6.87, and NH₂ as broad (about 1.0 ppm) singlet, centered at3.46 ppm, in the correct ratio: 2:2:1:1:1:2. Analysis: Calc. for C₂₇ H₁₈F₆ O₃ N₂ : C 60.9; H 3.38; F 2I.4; N 5.26; Found: C 61.3; H 3.19; F21.2; N 5.01%.

EXAMPLE 14 9-Phenyl-9-trifluormethyl-2,3,6,7-tetramethylxanthene (XVI)

A mixture of 32 g (0.14 mole) of 3,3'-di-o-xylyl ether (DXE), 25 g (0.14mole) trifluoroacetylbenzene, and 40 g (2 moles) HF was heated in ashaker tube at 140° for 8 hrs. After distilling off most of the HF, theresidue was transferred to a polyethylene jar containing excess cold 20%NaOH. The product was extracted with methylene chloride, the extractswere run through a short column packed with alumina, and stripped todryness. The pasty residue was stirred with methanol, and filtered. Theresulting solid was washed with methanol, and air-dried. It was purifiedfurther by sublimation at 200° /1 Torr, and then by recrystallizationfrom toluene. The product (XVI), obtained in 31 g (58%) yield, melted at214°-215°. Analysis: Calc. for C₂₄ H₂₁ F₃ O: C, 75.4; H, 5.50; F, 14.9;Found: C, 75.6; H, 5.52; F, 14.8%. NMR: d 7.40; quartet 7.30; s 6.96, s6.58, s 2.23, s 2.07 ppm in the correct 2:3:2:2:6:6 ratio. Repeatingthis run on larger scale (200 g trifluoroacetylbenzene) and lowertemperature (130°), improved the yield to 92%.

EXAMPLES 15 AND 169-Phenyl-9-(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic Acid (XVII)and 9-Phenyl-9-(trifluoromethyl)xanthene-2,3,6,7-dianhydride (XVII)

A 75 g sample (0.196 mole) of9-phenyl-9-trifluoromethyl-2,3,6,7-tetramethylxanthene (XVI) wasoxidized with potassium permanganate in two stages, as was done beforewith (III). This yield of air-dried crude tetraacid (XVII) was 75 g(76%). The crude tetraacid (XVII) was converted to the dianhydride(XVII) by heating under vacuum at 250°. The crude dianhydride (XVIII)can be sublimed in vacuo, and it also can be recrystallized fromanisole, as a bis-solvate (by NMR: the PX peaks are at 7.89 and 7.60ppm, in addition to anisole peaks). Purification of dianhydride (XVIII)was effected by high-precision sublimation in a McCarter sublimer. Aftera lower-melting foreshot, the main fraction was collected. It containedtwo different crystalline types: one consisted of clear light yellowcrystals of dianhydride (XVIII) of 99.9% purity, m.p. 276°, the othercomponent crystallized as opaque white clusters of needles. Purity ofdianhydride (XVIII) was in the 98.1-99.0% range. Analysis: Calc. for C₂₄H₉ F.sub. O₇ : C: 61.8; H 1.93; F 12.2; Found: C 61.9, H 2.03, F 11.8.

EXAMPLE 17 9-Phenyl-9pentafluoroethyl-2,3,6,7-tetramethylxanthene

A mixture of 101 g DXE and 100 g phenyl pentafluoroethyl ketone (both0.45 mole) was heated with 112 g (5.6 mole) HF in a shaker tube at 130°for 8 hrs. After venting off excess HF, the reaction mixture was pouredinto excess cold aqueous sodium hydroxide. The product was extractedwith a 50/50 mixture of methylene chloride and chloroform, the extractswere filtered through a 5-cm layer of alumina, and stripped. The residuewas stirred with methanol, and was filtered. There was obtained 173 g(89.6%) of crude9-phenyl-9-pentafluoroethyl-2,3,6,7-tetramethylxanthene. It wasrecrystallized from a 80/20 heptane/toluene mixture; m.p. 178°-179°. TheIR spectrum was sharp, and the NMR spectrum consisted of: d 7.43, asym.m 7.23, s 6.91, s(b) 6.66, s 2.20 and s 2.04 in the correct 2:3:2:2:6:6ratio. Analysis: Calc. C₂₅ H₂₁ F₅ O: C 69.4; H 4.86; F 22.0 ; Found: C69.5; H 4.92; F 22.5%.

EXAMPLE 18 9-Phenyl-9-perfluorooctyl-2,3,6,7-tetramethylxanthene

A mixture of 8.7 g of DXE and 20 g phenyl perfluorooctyl ketone (both0.038 mole) was heated with 0 g (0.5 mole) HF in a shaker tube at 130°for 8 hrs. After venting excess HF, the product mixture was poured intoexcess cold aqueous alkali, and was extracted with a 50/50 mixture ofmethylene chloride and chloroform. The extracts were filtered throughalumina, stripped and the residue was stirred with methanol. Filtrationyielded 9-phenyl-9-perfluorooctyl-2,3,6,7-tetramethylxanthene in twocrops, 6.9 and 1.1 g, for a total of 8.0 g (29% yield). The product wasrecrystallized from heptane; m.p. 177°-178°. NMR: d 7.41, m 7.28, s6.94, s(b) 6.67, s 2.24, s 2.07, in the correct 2:3:2:2:6:6 ratio.Analysis: Calc. for C₃₁ H₂₁ F₁₇ O: C 50.8; H 2.87; F 44.1; Found: C 508; H 2.94; F 44.1%.

EXAMPLE 19 9-Phenyl-9-Perluoropropyl-2.3.6.7-tetramethylxanthene

A mixture of 31.6 g phenyl perfluoropropyl ketone and 26 g DXE (both0.115 mole) was heated with 30 g (1.5 moles) HF for 8 hrs at 135°. Thereaction mixture was drowned in excess cold aqueous sodium hydroxide,extracted with a 50/50 methylene chloride and chloroform mixture; theextracts were filtered through alumina, stripped, and the residue wasstirred with excess methanol. The white solid was filtered, and wasobtained after drying in 24.9 g (44.9%) yield. After recrystallizationfrom toluene/heptane, the product melted at 189°-190°. NMR: d 7.43, m7.2-7.3, s 6.91, s(b) 6.66, s 2.23, s 2.07 in 2:3:2:2:6:6 ratio.Analysis: Calc. for C₂₆ H₂₁ F₇ O: C 64.7; H 4.36; F 27.6; Found: C 64.7;H 4.55; F 25.0, 25.1.

EXAMPLE 209-Trifluoromethyl-9-pentafluoroethyl-2,3,6,7-tetramethylxanthene

A mixture of 45.2 g DXE, 41 g trifluoromethyl pentafluoroethyl ketone(both 0.2 mole) and 50 g HF (2.5 moles) was heated in a shaker tube at140° for 8 hrs. After venting residual HF, the reaction mixture wastransferred to a polyethylene jar, containing icewater, plus excesssodium hydroxide. The product was extracted with methyIene chloride, theextracts were run through a bed of alumina, stripped, and the residuewas stirred with methanol, and filtered. There was obtained a total of18 g (21%) of white9-trifluoromethyl-9-pentafluoroethyl-2,3,6,7-tetramethylxanthene. It isvery soluble in toluene, chloroform, but insoluble in methanol. It waspurified by sublimation, and then recrystallized from heptane; m.p.139-140° . The NMR spectrum was confirmatory: s (b) 7.57; s 6.93 and s2.27 ppm in the correct 1:1:6 ratio. Analysis: Calc. for C₂₀ H₁₆ F₈ O: C56.6; H 3.77; F 35.85; Found: C.56.8; H 3.77; F 33.0, 33.1.

EXAMPLE 21 9-Phenyl-9-trifluoromethyl-2,7-dimenthylxanthene (XIX)

A mixture of 114 g (0.54 mole) p-tolyl ether (X), g (0.54 mole)trifluoromethyl phenyl ketone, and g (8 moles) HF was heated in anautoclave for 8 hrs at 130°. After venting excess HF, the reactionmixture was quenched in 2L ice water, containing 500 ml 50% NaOH. Theproduct was extracted with methylene chloride, the extracts werefiltered through a layer of alumina, stripped and distilled in vacuo.There was obtained 140 g (73%) of distillate boiling at 186°-210°/2Torr. The solid was recrystallized from methanol or isopropyl alcohol.M.p. 150°-151°. NMR: d 7.40, m 7.30, s 7.07, s(b) 6.64, s 2.16 ppm in2:3:4:2:6 ratio. AnaIysis: Calc. for C₂₂ H₁₇ F₃ O: C 74.6; H 4.80; F16.1; Found: C 74 7; H 4.90; F I5.g%.

EXAMPLE 22 9-Phenyl-9trifluoromethylxanthene-2,7-dicarboxvlic Acid (XX)

A 100 g batch of 9-phenyl-9-trifluoromethyl-2,7-dimethylxanthene (XIX)was oxidized in the same manner as a 75 g batch of (III). At the finalfiltration stage there was some granular white solid present in the MnO₂filter cake. It was extracted with methylene chloride, and identified asunreacted starting material. Yield of recovered (XIX) was 16 g. From thefiltrate, upon acidification with sulfuric acid there was obtained,after filtering, washing, and drying, 74 g (75%) of the dicarboxylicacid (XX). In another, larger scale preparation, the yield was 89%.

EXAMPLE 23 9- Phenyl-9-trifluoromethylxanthene-2,7-dicarbonyl Dichloride(XXI)

A slurry of 82 g (0.2 mole) of dried, crude-phenyl-9-trifluoromethylxanthene-2,7-dicarboxylic acid (XX) and 50 ml(large excess) of thionyl chloride in 500 ml chloroform was stirred andheated to gentle reflux in an oil bath. After 3 hrs of refluxing, thesolution became clear. It was stirred overnight, and allowed to cool.Volatiles were stripped at atmospheric pressure, 0 ml heptane plus someDarco was added to the residue, the mixture was heated to reflux, andfiltered through Celite. On cooling, crystals were obtained, which werefiltered off and washed with hexane.9-phenyl-9-trifluoromethylxanthene-2,7-dicarbonyl dichloride (XXI) wasobtained in 64.7 g (71.7%) yield. Another 10.7 g I2%) of the dichloridewas obtained by stripping the filtrate, and short-path distillation atabout 200°/0.8 Torr, and stirring the syrupy distillate with heptane.After two recrystallizations from heptane the product melted at128°-130°. IR: very strong carbonyl at 1750 cm⁻¹. NMR: dd 8.15, "s"7.74, m 7.3-7.5 ppm in 2:7(5+2) ratio.

EXAMPLE 24 9-Phenyl-9-trifluoromethylxanthene-2 7-dicarbonyl azide

To a stirred solution of 5.0 99-phenyl-9-trifluoromethylxanthene-dicarbonyl dichloride (XXI) in mlmethylene chloride was added an aqueous solution of 5 g (large excess)sodium azide plus 0.05 g tetrabutylammonium bromide (as phase transferagent). The two-phase mixture was stirred vigorously for 2 hrs, then theorganic layer was separated, and filtered through a small bed ofalumina. On evaporation, there was obtained 4.5 g of a white solid,which showed a strong azide band at 2140 cm⁻¹ and a strong carbonyl bandat 1685 cm⁻¹. NMR: d 8.04, "s" 7.62, m 7.37, d 7.30 ppm in the correct2:2:5:2 ratio. The compound melts with vigorous bubbling at 126°-127°.

EXAMPLE 25 9-Phenyl-9-trifluoromethylxanthene-2,7- diisocyanate (XXII)

A two phase system, consisting of 45 g (0.1 mole) of9-phenyl-9-trifluoromethylxanthenedicarbonyl dichloride (XXI) in 300 mlmethylene chloride, and 22 g sodium azide plus 0.5 g Bu₄ NBr in 100 mlwater was stirred vigorously at room temperature for 1.5 hr. The orangeorganic layer was separated, stirred with Darco, and filtered through aCelite/alumina layer. The colorIess fiIrrate was added dropwise toboiling toluene in a closed system, so that the solvent distilled out,and the nitrogen evolved could be measured by a wet-test meter. Afterall methylene chloride had distilled out and the toluene was refluxing,the theoretical amount of nitrogen was evolved. Toluene was distilledout at reduced pressure. The residue was extracted with 200 ml ofboiling heptane. On cooling the solution, crystals were obtained in twocrops 27.4 g and 7.8 g, for a total of 35.2 g (86.3%) of9-phenyl-9-trifluoromethylxanthene2,7-diisocYanate (XXII). The compoundmelts at 133°-134°, and contains a very strong NCO band at 2260 cm⁻¹.NMR: m 7.37, d 7.15, dd 7.06, "s" 6.56 (10 in 5:2:2:2 ratio. Analysis:Calc. for C₂₂ H₁₁ F₃ N₂ O₃ : C 64.7; H 2.70; F 14.0; Found: C 64.9; H2.91; F 13.8%.

EXAMPLE 269-(4-Perfluorohexylphenyl)-9-heptafluoropropyl-2,3,6,7-tetramethylxanthene

A mixture of 25.1 g dixylyl ether (0 11 mole) and g4-perfluorohexylphenyl heptafluoropropyl ketone (0.11 mole) was heatedwith 35 g (1.75 moles) HF in an autoclave at 140° C. for 8 hrs. Afterremoval of excess HF the clave contents were transfered into a jarcontaining excess ice and sodium hydroxide. The product was extractedwith methylene chloride, and the extracts were filtered through a bed ofalumina, and stripped to dryness. The residue was stirred with methanol,and filtered yielding 60 g (68%) of the product in two crops (56.4 g,and 3.6 g). The material can be recrystallized from heptane or fromisopropyl alcohol; M.p. 121°-122° C. It can also be distilled in vacuo.NMR: A₂ B₂ doublet 7.55, s 6.95, s 6.58, s 2.23 and s 2.07 ppm in thecorrect 4:1:1:3:3 ratio.

EXAMPLE 27 9,9-Bis(trifluoromethyll)-3,6-dihydroxyxanthene polyester(IX)

A solution of 7.020 g of 9,9-bis(trifluoromethyl)3,6-dihydroxyxanthene(VII) and 6.5 ml of triethylamine in 50 ml of methylene chloride wasstirred at room temperature as 4.070 g of a 70:30 mixture ofisophthaloyl chloride and terephthaloyl chloride in 20 ml of methylenechloride was added over 5 min. The mixture became cloudy and was stirredat reflux for one hour, and then at room temperature overnight. Thesolution was added to 500 ml of methanol in a blender; the precipitatedpolymer was filtered, reblended with 500 ml of fresh methanol, andfiltered again. The polymer was then blended with warm tap water,filtered, washed with methanol and dried to yield 9.2 g of polyester; uinh =0.37 (0.4% in NMP). Film was cast from a 15% solution of polymer inTHF and the solvent was removed in a vacuum oven at 130° . The film wastested for oxygen and nitrogen separation at 500 psig (feed gas: 21% O₂/79% N₂): the O₂ /N₂ separation factor was 4.50 and the oxygenpermeability was 7.0 Barrers. The film was fairly strong even at thislow molecular weight.

I claim:
 1. A monomer of the formula ##STR10##